In general, the distillers solubles are generally deformed as, for example, distillation residues soluble or suspended in water and from which the rough parts of the particles have been removed, such residues being from stillage (residue of distillation) of whisky and so on, and they may be dried into dried solubles or concentrated or made into semisolid state and added to feed, thus having been broadly utilized.
Also, these distillers solubles have been known for their effects as a growth source of Actinomyces and other various microorganisms or as a growth promoting factor and thereby have been broadly used.
However, even such useful distillers solubles have large drawbacks in use. For example, in the case where the distillers solubles are used as growth source of microorganisms, as they are or in concentrated state, many suspended contaminants and lipid materials may contaminate the microorganisms cells or products; but the removing thereof is very difficult, so that they can not be possibly used for propagation of cells which are adapted for food, such as bakers yeast, starter and so on as they are. Also such distillers solubles have never been utilized for products which are difficult to purify. Moreover, the distillers solubles concentrated and formed into solid state have poor solubility, and in use they are inconvenient, so that they have been difficult to use as a general source of culture.
Heretofore, the distillers solubles sold in market generally are those produced by removing large solids from stillage of whisky or the like, and concentrated, and it has been believed that the distillers solubles themselves constitute an available component as a whole.